With a view to form ultrafine copper wiring in a semiconductor device, there is proposed a method of forming a barrier film, which is composed of a manganese silicate (MnSiO3 or Mn2SiO4) film. In this method, a manganese metal film is formed by depositing a manganese metal on a silicon-containing oxide film formed on a substrate through use of a CVD (Chemical Vapor Deposition) method using a manganese precursor. Then, the substrate having the manganese metal film formed thereon is annealed for five minutes at a temperature of 300 to 400 degrees C. under an atmosphere added with a small amount of oxygen. Thus, the manganese metal becomes a silicate by reacting with silicon and oxygen of the underlying silicon-containing oxide film, whereby a manganese silicate film is formed.
In this method, the annealing is performed after forming a copper film on a manganese metal film.
Examples of manganese precursors used in the CVD method include: a cyclopentadienyl-based manganese compound, e.g., (EtCp)2Mn(bis(ethyl cyclopentadienyl)manganese); an amidinate-based manganese compound, e.g., bis(N,N′-dialkylacetamininate) manganese expressed by a chemical formula Mn(R1N—CR3—NR2)2; and an amideaminoalkane-based manganese compound, e.g., bis(N,N′-1-alkylamide-2-dialkylaminoalkane) manganese expressed by a chemical formula Mn(R1N—Z—NR22)2. In the chemical formulae noted above, “R”, “R1”, “R2” and “R3” are functional groups described by —CnH2n+1 (where n is an integer of 0 or greater) and “Z” is a functional group described by —CnH2n—(where n is an integer of 0 or greater).
As a method of depositing a manganese metal, an ALD (Atomic Layer Deposition) method as well as the CVD method is studied.
As copper wiring becomes finer, it is required to make a barrier film thinner. However, if a manganese metal film is formed by depositing a manganese metal on a silicon-containing oxide film as an underlying layer through the use of a CVD method, it was found that, at an initial film forming stage, manganese agglomerates into a granular shape and does not form a continuous thin film. For that reason, if an attempt is made to obtain a barrier film of, e.g., several nanometers in thickness, by forming a thin manganese metal film and then converting the manganese metal film into a silicate, the resulting film is not a continuous thin film and does not serve as a barrier film. Furthermore, a barrier film composed of a manganese silicate film cannot be said to have sufficiently high adhesion to an upper layer metal film (e.g., a copper film).